Fuel injectors have been developed for gas turbine engines to reduce combustion emissions, such as smoke and nitrogen oxide emissions. For example, the Coburn U.S. Pat. No. 4 290 558 issued Sep. 27, 1981 describes gas turbine fuel nozzle capable of operating in a fuel/water injection mode for smoke reduction purposes.
The Bradley U.S. Pat. No. 4 600 151 issued Jul. 15, 1986 describes an airblast fuel injector capable of operating in dual fuel, alternate fuel, or fuel/water modes for thrust augmentation and emissions reduction purposes. Airblast fuel injectors are designed to achieve atomization of a film of liquid fuel formed on a fuel discharge orifice surface by directing high velocity airflow supplied to the injector from the engine compressor at the fuel film as it leaves the orifice surface. Typically, the atomizing airflow is directed at both sides of the fuel film leaving the orifice surface. Such airblast fuel injectors are described further in the Helmrich U.S. Pat. No. 3 684 186 issued Aug. 15, 1972 and the Simmons et al U.S. Pat. No. 3 980 233 issued Sep. 14, 1976.
With the development of lower emission gas turbine engines, there is an increased requirement for fuel injectors that can provide more uniform fuel dispersion and higher rate of fuel/air mixing in the combustor environment. This situation adversely affects the qualification of current airblast injectors for low-emission gas turbine applications. Current airblast injectors are susceptible to higher levels of combustion emissions due to their limited capability in fuel dispersion and fuel/air mixing and therefore are less satisfactory for low-emission applications. In view of the desire in the gas turbine industry for lower emission engines, there is a need to provide airblast injectors capable of satisfactorily atomizing and distributing the fuel flow to reduce the emission level from the gas turbine engine.
The present invention has an object to satisfy this need by providing an improved airblast fuel injector capable of reducing combustion emissions from the engine via enhanced fuel atomization and distribution as well as fuel/air mixing.